The present invention relates in general to the field of lithography. More specifically, embodiments of the present invention relate to the determination of the consistency and uniformity of lithography effective dose.
Lithography is a process used to transcribe a pattern, such as an integrated circuit pattern, or the like, onto a substrate. Lithography includes an exposure process in which a layer of resist (also known as photoresist) on a substrate is exposed to radiation that could be electrons, ions, soft x-ray (a.k.a. EUV) photons or optical photons modulated by a patterned mask. The photoresist is then developed to remove the exposed portion thereof (in the case of a positive photoresist) or non-exposed portion thereof (in the case of a negative photoresist), thereby forming a photoresist pattern. Then, a layer of material lying under the photoresist pattern is etched using the photoresist pattern as a mask. As a result, a pattern corresponding to the pattern of the mask is transcribed onto the substrate. The pattern can be used to create integrated circuit structures.
The dose and intensity of the exposure radiation should be controlled to be uniform during the exposure process. To this end, feedback relevant to the exposure radiation can be evaluated to determine the consistency and uniformity of the lithography process. In this respect, it becomes desirable to accurately characterize the exposure energy being delivered to the substrate. Control of the resist post-exposure bake and develop conditions are also important to ensure consistent dose response. It would be desirable to determine the repeatability and uniformity of the lithography process. In this respect, it becomes desirable to accurately characterize the effective dose delivered to the substrate, including the impacts of exposure dose and the post-exposure bake and develop processes.